// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.

#include "leveldb/filter_policy.h"

#include "util/coding.h"
#include "util/logging.h"
#include "util/testharness.h"
#include "util/testutil.h"

namespace leveldb {

    static const int kVerbose = 1;

    static Slice Key(int i, char *buffer) {
        EncodeFixed32(buffer, i);
        return Slice(buffer, sizeof(uint32_t));
    }

    class BloomTest {
    private:
        const FilterPolicy *policy_;
        std::string filter_;
        std::vector<std::string> keys_;

    public:
        BloomTest() : policy_(NewBloomFilterPolicy(10)) {}

        ~BloomTest() {
            delete policy_;
        }

        void Reset() {
            keys_.clear();
            filter_.clear();
        }

        void Add(const Slice &s) {
            keys_.push_back(s.ToString());
        }

        void Build() {
            std::vector<Slice> key_slices;
            for (size_t i = 0; i < keys_.size(); i++) {
                key_slices.push_back(Slice(keys_[i]));
            }
            filter_.clear();
            policy_->CreateFilter(&key_slices[0], static_cast<int>(key_slices.size()),
                                  &filter_);
            keys_.clear();
            if (kVerbose >= 2) DumpFilter();
        }

        size_t FilterSize() const {
            return filter_.size();
        }

        void DumpFilter() {
            fprintf(stderr, "F(");
            for (size_t i = 0; i + 1 < filter_.size(); i++) {
                const unsigned int c = static_cast<unsigned int>(filter_[i]);
                for (int j = 0; j < 8; j++) {
                    fprintf(stderr, "%c", (c & (1 << j)) ? '1' : '.');
                }
            }
            fprintf(stderr, ")\n");
        }

        bool Matches(const Slice &s) {
            if (!keys_.empty()) {
                Build();
            }
            return policy_->KeyMayMatch(s, filter_);
        }

        double FalsePositiveRate() {
            char buffer[sizeof(int)];
            int result = 0;
            for (int i = 0; i < 10000; i++) {
                if (Matches(Key(i + 1000000000, buffer))) {
                    result++;
                }
            }
            return result / 10000.0;
        }
    };

    TEST(BloomTest, EmptyFilter) {
        ASSERT_TRUE(!Matches("hello"));
        ASSERT_TRUE(!Matches("world"));
    }

    TEST(BloomTest, Small) {
        Add("hello");
        Add("world");
        ASSERT_TRUE(Matches("hello"));
        ASSERT_TRUE(Matches("world"));
        ASSERT_TRUE(!Matches("x"));
        ASSERT_TRUE(!Matches("foo"));
    }

    static int NextLength(int length) {
        if (length < 10) {
            length += 1;
        } else if (length < 100) {
            length += 10;
        } else if (length < 1000) {
            length += 100;
        } else {
            length += 1000;
        }
        return length;
    }

    TEST(BloomTest, VaryingLengths) {
        char buffer[sizeof(int)];

        // Count number of filters that significantly exceed the false positive rate
        int mediocre_filters = 0;
        int good_filters = 0;

        for (int length = 1; length <= 10000; length = NextLength(length)) {
            Reset();
            for (int i = 0; i < length; i++) {
                Add(Key(i, buffer));
            }
            Build();

            ASSERT_LE(FilterSize(), static_cast<size_t>((length * 10 / 8) + 40))
                    << length;

            // All added keys must match
            for (int i = 0; i < length; i++) {
                ASSERT_TRUE(Matches(Key(i, buffer)))
                        << "Length " << length << "; key " << i;
            }

            // Check false positive rate
            double rate = FalsePositiveRate();
            if (kVerbose >= 1) {
                fprintf(stderr, "False positives: %5.2f%% @ length = %6d ; bytes = %6d\n",
                        rate * 100.0, length, static_cast<int>(FilterSize()));
            }
            ASSERT_LE(rate, 0.02);   // Must not be over 2%
            if (rate > 0.0125) mediocre_filters++;  // Allowed, but not too often
            else good_filters++;
        }
        if (kVerbose >= 1) {
            fprintf(stderr, "Filters: %d good, %d mediocre\n",
                    good_filters, mediocre_filters);
        }
        ASSERT_LE(mediocre_filters, good_filters / 5);
    }

// Different bits-per-byte

}  // namespace leveldb

int main(int argc, char **argv) {
    return leveldb::test::RunAllTests();
}
